4-Aryl-1-carbamoyl-2-tetrazoline-5-thione stabilizer precursor in a heat stabilizable photographic element

ABSTRACT

A 4-aryl-1-carbamoyl-2-tetrazoline-5-thione stabilizer precursor in a heat stabilizable photographic element or composition provides increased image stability upon heat processing of the element or composition. This stabilizer precursor is useful in photothermographic materials, for example, comprising a photosensitive silver salt and an oxidation-reduction imageforming combination comprising a heavy metal salt oxidizing agent with a reducing agent.

United States Patent Burness et al.

Assignee: Eastman Kodak Company, Rochester, NY.

Filed: Jan. 23, 1974 Appl. No.: 435,806

US. Cl. 96/61 R; 96/48 HD; 96/66 T; 96/76 R; 96/95; 96/109; 96/1 14.] Int. Cl G03c 5/24 Field of Search... 96/48 HD, 109, 114.1, 61 R, 96/66 T, 76 R, 95

References Cited FOREIGN PATENTS OR APPLICATIONS 7/1971 Belgium 96/48 HD July 8, 1975 OTHER PUBLICATIONS Research Disclosure, 4/74, No. 12044.

[57] ABSTRACT A 4-aryl-I-carbamoyl-2-tetrazoline-5-thione stabilizer precursor in a heat stabilizable photographic element or composition provides increased image stability upon heat processing of the element or composition. This stabilizer precursor is useful in photothermographic materials, for example, comprising a photo sensitive silver salt and an oxidation-reduction imageforming combination comprising a heavy metal salt oxidizing agent with a reducing agent.

38 Claims, No Drawings 4-ARYL-l-CARBAMOYL-2-TETRAZOLINE-5- THIONE STABILIZER PRECURSOR IN A HEAT STABILIZABLE PHOTOGRAPHIC ELEMENT BACKGROUND OF THE INVENTION Field of the Invention This invention relates to certain 4-aryl-l-carbamoyl- Z-tetrazoline-S-thione stabilizer precursors in photographic elements, compositions and processes to provide improved stable images. In one of its aspects it relates to a heat-stabilizable photographic element comprising a photosensitive silver salt and the described thione stabilizer precursor. In another of its aspects it relates to photothermographic elements comprising a so-called oxidation-reduction image-forming combination comprising a silver salt oxidizing agent with a reducing agent and photosensitive silver halide with the described thione stabilizer precursor. in another of its aspects it relates to a photothermographic composition comprising the described thione stabilizer precursor. A further aspect relates to a method of stabilizing an image in a photothermographic element comprising a photosensitive silver salt and a thione stabilizer precursor as described by overall heating the exposed element.

Description of the State of the Art It is known to obtain an image in a photosensitive element by so-called dry processing with heat. The photothermograhic element can contain a reducing agent, a light-insensitive silver salt of an organic acid, such as silver behenate, as an oxidizing agent and a low concentration of photographic silver halide. Such photothermographic elements are described, for example, in U.S. Pat. No. 3,457,075 of Morgan et al., issued July 22, 1969; U.S. Pat. No. 3,152,904 of Sorensen et al., issued Oct. 13, 1964; British Pat. No. 1,161,777 published Aug. 20, 1969 as well as in Research Disclosure, January, 1973, pages 16-21.

In a heat-developable photographic element, one of the main difficulties involves post-processing stability. Because these heat-developable elements are suitable for so-called dry processing with heat and are designed to eliminate a fixing step which would normally remove undeveloped silver, it is necessary that a means be provided for post-processing stabilization to enable roomlight handling.

Several means have been proposed, such as l washing with water to remove undeveloped silver salts, (2) heating to release a Bronstead or Lewis acid such as HCl, BF or HF from compounds such as mnitrobenzenesulfonyl chloride, para-toluene sulfonic acid urea addition complex or pacetamidobenzenediazonium fluoroborate and (3) chelation of the oxidizing agent with, for example, salicylaldoxime or benzotriazole as described in U.S. Pat. No. 3,152,904 of Sorensen et al., issued Oct. 13, 1964. Another method proposed for solving the problem of post-processing instability is to provide a photothermographic combination in which the oxidationreduction image-forming combination is on one sheet of material and the latent image forming photographic silver halide on a separate sheet. The sheets are separated after exposure such as described in U.S. Pat. No. 3.152.904. A further means proposed for stabilization in U.S. Pat. No. 3,152,904 involves swabbing a 1% solution of phenylmercaptotetrazole onto the surface of the overall heated photothermographic material or rubbing benzotriazole into the surface of the coating. These proposed means for stabilization are not useful for large volume handling of heat-developable photographic elements.

It has also been proposed to provide stabilized images in heat-developable materials by treating the developed image with a solution containing certain thiol or thione compound stabilizers. This is described, for example, in U.S. Pat. No. 3,617,289 of Ohkubo et al., issued Nov. 2, 1971. One of the compounds proposed for this solu' tion stabilization is l-phenyl-5-mercaptotetrazole. While l-phenyl-5-mercaptotetrazole has been proposed for use in heat-developable photographic elements as described in British Pat. No. 930,572 published July 3, 1963 and U.S. Pat. No. 3,312,550 issued Apr. 4, 1967 and indicated in the discussion of the art in U.S. Pat. No. 3,700,457 issued Oct. 24, 1972, unfortunately the addition of this compound to photographic silver compositions provides undesired desensitization at concentrations which produce stabilization of a developed image.

Another means of stabilization of an image in a photothermographic material is described in copendin g U.S. application Ser. No. 249,260 of Hiller, filed May 1, 1972 which is a continuation-in-part application of U.S. Ser. No, 43,171 of Hiller, filed June 3, 1970, now abandoned. Certain stabilizer precursors which are azole thioethers or blocked azoline thiones are employed in photothermographic materials according to the description in these applications. An example of a stabilizer precursor proposed in photothermograhic materials is S-methoxycarbonylthio-l-phenyltetrazole. As illustrated in following comparative Example 16, this compound does not always provide the desired increased stability of a heat-developed image. The subject matter of described U.S. application Ser. No. 43,171 of l-liller, filed June 3, 1970 is published in Belgian Pat. No. 768,071 published July 30, 1971.

While various S-mercaptotetrazole compounds are known in photographic materials for various purposes, such as described in British Pat. No. 1,238,928 published July 14, 1971, and other of the described patents, none of the mentioned art suggests a useful solution to the continuing need for improved heatdevelopable, thione compound containing, photographic materials providing improved post-processing stability.

Accordingly, there has been a continuing need for heat-developable photographic materials, especially photothermographic materials comprising an imageforming combination containing a silver salt oxidizing agent, such as silver behenate, with a reducing agent, and photosensitive silver halide, which has improved post-processing image stability, that is reduced background density, when employing a thione stabilizer precursor.

Summary of the invention The described improvements are provided in a heatstabilizable photographic element or composition by employing as a thione stabilizer precursor a 4-aryl-lcarbamoyl-Z-tetrazoline-S-thione stabilizer precursor. This thione stabilizer precursor is especially useful in a photothermographic material comprising a photosensitive silver salt and an oxidation-reduction imageforming combination comprising (i) a heavy metal salt oxidizing agent, such as silver behenate and silver stearate, with (ii) a reducing agent.

The described improvements are provided, for example, in a photothermographic element comprising a support having thereon a layer comprising (a) photosensitive silver halide, (b) an oxidation-reduction image-forming combination comprising (i) a silver salt oxidizing agent, such as silver behenate and silver stearate, with (ii) a reducing agent, (c) a polymeric binder, and (d) a thione, image stabilizer precursor comprising a 4-aryl-1-carbamoyl-Z-tetrazoline-S-thione, as described herein.

Detailed Description of the Invention A variety of 4-aryl-1-carbamoyl-2-tetrazoline-5- thione stabilizer precursors can be employed in the practice of the invention to provide improved postprocessing stability without adversely affecting desired properties of the heat-developable photographic material.

A test can be used to determine whether or not a compound or material is a useful image stabilizer precursor as described. While different tests can be employed to determine useful image stabilizer precursors depending upon the particular heat-developable photographic element and composition, a desired image, processing conditions and the like, one test which can be employed for certain photothermographic elements is described in following Example 14. Useful materials or compounds, after incorporation in the photothermographic element as described in Example 14 and after imagewise exposure and overall heating of the element as described, prevent the buildup of background density or minimum density above 0.10 density unit more than the original minimum density without undesired stain and without significantly adversely affecting maximum density, in comparison to a control photothermographic element as described in Example 14.

It is believed that the described tetrazoline-S-thione compounds are precursors of the moiety, compound or material which prevents undesired decreased stability due to room-light exposure. However, the exact mechanism of stabilization is not fully understood.

A useful stabilizer precursor according to the invention is a 4-aryl-1-carbamoy1-2-tetrazoline-S-thione represented by the formula:

wherein R is aryl, such as aryl containing 6 to 12 carbon atoms, including phenyl and naphthyl; and R is alkyl containing 1 to 12 carbon atoms, such as 1 to 6 carbon atoms, aryl, such as aryl containing 6 to 12 carbon atoms, including phenyl and naphthyl, cycloalkyl containing 3 to 8 carbon atoms, such as cyclohexyl and cyclopropyl, when n is l; or alkylene containing 1 to 10 carbon atoms when n is 2, such as alkylene containing 1 to 6 carbon atoms including methylene and ethylene; and n is 1 or 2.

Useful stabilizer precursors within the described formula include, for instance:

4-phenyll -phenylcarbamoyl-Z-tetrazoline-S-thione,

l-cyclohexylcarbamoyl-4-phenyl-2-tetrazoline-5- thione, l-methylcarbamoyl-4-phenyl-2-tetrazoline-5-thione, l-hexylcarbamoyl-4-phenyl-2-tetrazoline 5-thione,

N,N-hexylmethylenebis( l-carbamoyl4-phenyl-2-tetrazoline-S-thione), l-butylcarbamoyl-4-phenyl-2-tetrazoline-S-thione, di-2-(4-phenyl-5-thioxo-2-tetrazolin-1- ylcarbonylamino)-ethyl fumarate The described tetrazoline-S-thione compounds can be prepared by reacting 1phenyl-2-tetrazoline-5- thione in a suitable solvent in the presence of a catalyst such as heptamethylisobiguanide, with a suitable isocyanate compound. The preparation of lcyclohexylcarbamoyl-4-pheny1-2-tetrazoline-S-thione is typical of a useful preparation. Typical preparations of compounds according to the invention are described in following Examples 1-5. It is preferred that the resulting product be purified such as by treatment with solvents and other typical purification means.

The described stabilizer precursors of the invention are useful in a variety of heat-developable photographic materials. Typically, useful heat stabilizable, photographic elements in which the described stabilizer precursors are useful comprise a support having thereon a photosensitive silver salt, a photosensitive silver salt developing agent and a 4-aryl-l-carbamoyl-2- tetrazoline-S-thione stabilizer precursor.

The useful concentration of stabilizer precursor according to the invention will depend upon different factors such as the particular photographic element, processing temperatures, particular components of the photographic element, desired image and the like. A useful concentration of stabilizer precursor according to the invention is about 0.009 mole to about 0.034 mole of the described stabilizer precursor per mole of total silver in the described photographic element. The optimum concentration useful can be determined based on the described factors.

Typical photographic elements in which the stabilizer precursors of the invention are useful are described, for example, in US. Pat. No. 3,457,075 of Morgan et 211., issued July 22, 1969; US. Pat. No. 3,152,904 of Soren sen et al., issued Oct. 13, 1964; U.S. Pat. No. 3,429,706 of Shepard et al., issued Feb. 25, 1969; US. Pat. No. 3,672,904 of deMauriac, issued June 27, 1972 and Research Disclosure, January, I973, pages 16-21.

The stabilizer precursors of the invention are especially useful in photothermographic materials comprising photosensitive silver halide, an oxidation-reduction image-forming combination comprising (i) silver behenate, with (ii) a sulfonamidophenol reducing agent, a poly(vinyl butyral) binder, a spectral sensitizing dye, and a toning agent (also known as an activator-toning agent) comprising succinimide or N- hydroxynaphthalimide. Such a photothermographic material is described, for example, in Research Disclosure, January, 1973, pages 16-21.

An especially useful embodiment of the invention is a photothermographic element comprising a support having thereon a layer comprising (a) photosensitive silver halide, (b) an oxidation-reduction image-forming combination comprising (i) silver behenate, with (ii) a sulfonamidophenol reducing agent, (c) a poly( vinyl butyral) binder, (d) a spectral sensitizing dye, (e) a toning agent. such as succinimide or N- hydroxynaphthalimide, and (f) lcyclohexylcarbamoyl-4-phenyI-Z-tetrazoline-S-thione.

The described photographic materials according to the invention comprise a photosensitive component which is typically a photosensitive silver salt, such as photosensitive silver halide. In the photothermographic materials comprising the described oxidation-reduction image-forming combination, it is believed that the photosensitive salt or a component resulting from the photosensitive salt acts as a catalyst for the described oxidation-reduction image-forming combination. A typical concentration range of photosensitive component, especially photosensitive silver salt. such as photosensitive silver halide, is from about 0.0l mole to about 20.0 moles of photosensitive component per mole of heavy metal salt oxidizing agent, for example, per mole of silver salt oxidizing agent. An especially useful photosensitive component is a photosensitive silver halide because it is highly photosensitive. Useful photosensitive silver salts, however, include silver-dye complexes and combinations of photosensitive silver halide with other photosensitive silver salts. Preferred photosensitive silver halides are silver chloride, silver bromide, silver bromoiodide, silver chlorobromoiodide or mixtures thereof. Very fine-grain photosensitive silver halide is especially useful although coarse or finegrain photosensitive silver halide can be employed if desired. The photosensitive silver halide can be prepared by any of the procedures known in the photographic art. Such procedures and forms of photosensitive silver halide are described, for example, in the Product Licensing Index, Volume 92, December, l971, publication 9232 at page I07, paragraph I. The photosensitive silver halide according to the invention can be unwashhed or washed, can be chemically sensitized, can be protected against the production of fog and stabilized against loss of sensitivity during keeping, as described in the above Product Licensing Index publication.

The photothermograhic elements and compositions according to the invention typically comprise an oxidation-reduction image-forming combination which contains an oxidizing agent, preferably a heavy metal salt oxidizing agent. The heavy metal salt oxidizing agent can be a heavy metal salt of an organic acid such as a fatty acid which is resistant to darkening upon illumination. An especially useful class of heavy metal salts of organic acids is represented by the water insoluble silver salts of long chain fatty acids which are stable to light. Compounds which are suitable silver salt oxidizing agents include: silver behenate, silver stearate, silver oleate. silver laurate, silver hydroxystearate, silver caprate, silver myristate and silver palmitate. Silver salts can be employed as the heavy metal salt oxidizing agent which are not silver salts of long-chain fatty acids. Such silver salt oxidizing agents which are useful include, for example, silver benzoate, silver benzotriazole, silver terephthalate, silver phthalate and the like.

The described photothermographic elements and compositions can comprise various reducing agents. Suitable reducing agents which can be employed with the described stabilizer precursors include substituted phenols and naphthols. for example, bis-betanaphthols. Suitable bis-beta-naphthols include, for example. 2.2 '-dihydroxy-1 l '-binaphthyl, 6,6'-dibromo- 2.2 '-dihydroxyl ,l binaphthyl, 6,6'-dinitro-2,2 '-dihydroxy-l .1 '-binaphthyl and/or bis-(2-hydroxy-lnaphthyl) methane. Other reducing agents which can be employed in photothermographic elements, according to the invention, include polyhydroxybenzenes such as hydroquinone, alkyl-substituted hydroquinones such as tertiary butylhydroquinone, methylhydroquinone, 2,5-dimethylhydroquinone and 2,6-dimethylhydroquinone; catechols and pyrogallols, chloro-substitutecl hydroquinones such as chlorohydroquinone or dichlorohydroquinone; alkoxy-substituted hydroquinone such as methoxyhydroquinone or ethoxyhydroquinone; aminophenol developing agents, such as 2,4- diaminophenols and methylaminophenols; ascorbic acid developing agents such as ascorbic acid, ascorbic acid ketals and ascorbic acid derivatives; hydroxylamine developing agents; 3-pyrazolidone developing agents such as l-phenyl-3-pyrazolidone and 4-methyl- 4-hydroxymethyl-l-phenyl-S-pyrazolidone and the like. Combinations of reducing agents can be employed if desired.

Especially useful reducing agents which can be employed in the photothermographic materials according to the invention are sulfonamidophenol reducing agents as described in Research Disclosure, January, l973, pages 16-21. One especially useful class of sulfonamidophenol reducing agents is represented by the formula:

wherein R is phenyl, naphthyl, methylphenyl, thienyl, quinolinyl, thiazyl, or alkyl containing 1 to 4 carbon atoms, such as methyl, ethyl, propyl or butyl; R is hydrogen, R' SO NH, alkoxy containing 1 to 4 carbon atoms, such as methoxy, ethoxy, propoxy and butoxy, bromo or chloro; R is hydrogen, bromo, chloro, alkyl containing 1 to 4 carbon atoms, as described, or alkoxy containing 1 to 4 carbon atoms, such as methoxy, ethoxy and propoxy. R, R and/or R can contain substitu ent groups which do not adversely affect the reducing properties of the described sulfonamidophenol reducing agents or the desired sensitometric properties of the photothermographic elements and materials of the invention. Examples of substituent groups which can be present are alkyl containing 1 to 3 carbon atoms such as methyl, ethyl and propyl, chloro, bromo and phenyl. In some cases, it is desirable to avoid an amino group as a substituent. The amino group, in some cases, provides an overly active reducing agent. sulfonamidophenol reducing agents, as described, include sulfonamidonaphthols. A sulfonamidonaphthol which is useful is represented by the formula:

phenols which contain two sulfonamido groups are more active compounds within the sulfonamido reducing agent class. The sulfonamidophenols containing two or more sulfonamido groups are employed for shorter developing times or with heavy metal salt oxidizing agents which are less active than silver behenate. In some cases image discrimation provided by photothermographic materials containing the sulfonamidonaphthols and trifunctional sulfonamidophenols is less than that provided by other of the described sulfonamidophenols.

It is desirable, in some cases, to employ a so-called toning agent, also known as an accelerator-toning agent or activator-toning agent, in the photothermographic materials of the invention. Useful toning agents are described, for example, in Belgian Pat. No. 766,590 issued June 15, 1971 and in Research Disclosure, .lanuary, I973, pages l6-2l. Combinations of toning agents can be employed in the photothermographic materials according to the invention if desiredv Typical toning agents include, for example, phthalimide, N- hydroxyphthalimide, N-potassium phthalimide, succinimide, N-hydroxy-l,S-naphthalimide and/or N- hydroxysuccinimide. In some cases other toning agents can be employed such as l-(ZHiphthalazinone and 2- acetylphthalazinone and the like.

It is desirable, in some cases, to employ a combination of stabilizers in the photothermographic materials of the invention. In addition to combinations of stabilizers within the described formula according to the invention, other image stabilizers or stabilizer precursors can in some cases be employed with the stabilizer precursors of the invention. Typical stabilizer precursors which can be employed in combination with the tetrazoline-5thione stabilizer precursors of the invention include, for example, azole thioethers and blocked 2120- line thione stabilizer precursors as described in Belgian Pat. No. 768,07l issued July 30, l97l.

A photothermographic element or composition as described according to the invention can contain various colloids alone or in combination as vehicles, binding agents and in various layers. Suitable materials can be hydrophobic or hydrophilic. They are transparent or translucent and include both naturally-occurring substances such as proteins, for example, gelatin, gelatin derivatives, cellulose derivatives, polysaccharides such as dextran, gum arabic and the like; and synthetic polymeric substances such as water soluble polyvinyl compounds like poly(vinylpyrrolidone), acrylamide polymers and the likev Other synthetic polymeric compounds which can be employed include dispersed vinyl compounds such as in latex form and particularly those which increase dimensional stability of photographic materials. Effective polymers include water-insoluble polymers of alkyl acrylates and methacrylates, acrylic acid, sulfoalkyl acrylates, methacrylates and those which have crosslinking sites which facilitate hardening or curing as well as those having recurring sulfobetaine units as described in Canadian Pat. No. 774,054. Especially useful high molecular weight materials and resins include poly(vinyl butyral), cellulose acetate butyrate, poly(methyl methacrylate), poly(vinylpyrrolidone), ethylcellulose, polystyrene, poly(vinyl chloride), chlorinated rubber, polyisobutylene, butadiene-styrene copolymers, vinyl chloride-vinyl acetate copolyrners, copolymers of vinyl acetate, vinyl chloride and maleic acid and poly(vinyl alcohol).

The useful concentration of reducing agent according to the invention will vary depending upon the particular photographic element, desired image, processing conditions, particular stabilizer precursor employed and the like. A useful concentration of reducing agent is typically from about 0.2 mole to about 2.0 moles of reducing agent per mole of photosensitive salt. A useful concentration of reducing agent in relationship to oxidizing agent, such as silver behenate or silver stearate, is typically from about 0.0! mole to about 20 moles of reducing agent per mole of oxidizing agent such as per mole of silver behenate in the photothermographic material. Reducing agents can be employed in combination. When combinations are employed, the total concentration of reducing agent is typically within the described concentration range.

Photothermographic elements according to the invention can contain development modifiers that function as speedincreasing compounds, hardeners, antistatic layers, plasticizers and lubricants, coating aids, brighteners, spectral sensitizing dyes, absorbing and filter dyes, also as described in the Product Licensing Index, Volume 92, December, l97l, publication 9232, pages l07-l 10.

The photothermographic elements according to the invention can comprise a wide variety of supports. Typical supports include cellulose nitrate film, cellulose ester film, poly(vinyl acetal) film, polystyrene film, poly(ethylene terephthalate) film, polycarbonate film and related films or resinous materials, as well as glass, paper, metal and the like supports which can withstand the processing temperatures employed according to the invention. Typically a flexible support is employed.

The photothermographic compositions and other compositions according to the invention can be coated on a suitable support by various coating procedures including dip coating, air knife coating, curtain coating or extrusion coating using hoppers such as described in US. Pat. No. 2,681,294 of Beguin, issued June 15, 1954. If desired, two or more layers can be coated simultaneously such as described in US. Pat. No. 2,76l,79l of Russell issued Sept. 4, 1956 and British Pat. No. 837,095.

Spectral sensitizing dyes can be used in the described photothermographic elements and compositions of the invention to confer additional sensitivity to the ele ments and compositions of the invention. Useful sensitizing dyes are described, for example, in the Product Licensing Index, Volume 92, December, 1971, publication 9232, pages l07-l 10, paragraph XV.

After imagewise exposure of the photographic element according to the invention, typically to visible light, the resulting latent image can be developed merely by overall heating the element to moderately elevated temperatures. This also provides postprocessing stabilization of the element. This overall heating merely involves heating the described element overall in the range from about 80 to about 250C. such as for about 0.5 to about 60 seconds. By increasing or decreasing the length of time of heating, a higher or lower temperature within the described range can be employed depending upon the desired image, particu lar stabilizer precursor, particular reducing agent, and the like. Typically, a lower processing temperature is desired. A preferred processing temperature range is from about 1 l5 to about [C. A developed amd stabilized image is typically produced within several seconds, such as from about 0.5 seconds to about 60 seconds.

Any suitable means can be used for providing the desired processing temperature range. The heating means can be a simple hot plate, iron, roller or the like.

Processing is usually carried out under ambient conditions of pressure and humidity. Conditions outside normal atmospheric pressure and humidity can be employed if desired.

The described stabilizer precursor according to the invention can be in any suitable location in the photographic material according to the invention which provides the desired stabilized image. If desired, one or more of the components of the photothermographic element according to the invention can be in one or more layers of the element. For example, in some cases it can be desirable to include certain percentages of the reducing agent, toner, image stabilizer precursor and- /or other addenda in a protective layer over the photothermographic element. This in some cases can reduce migration of certain addenda in the layers of the photothermographic element.

Another embodiment of the invention comprises a photothermographic composition or element comprising (a) photosensitive silver salt, such as photosensitive silver halide. (b) a photosensitive silver salt developing agent, as described, (c) a 4-aryl-1-carbamoyl-2-tetrazoline-S-thione stabilizer precursor, also as described, (d) a base-release agent, and (e) a polymeric binder.

A variety of base-release agents can be employed in the photographic materials according to the invention depending upon the particular photographic component, the particular stabilizer precursor, the desired image, processing temperature range, and the like. A base-release agent as employed herein is intended to mean a compound which releases base upon heating to a desired temperature to provide activation of at least one of the components of the photographic material, such as activation of the reducing agent. Typical baserelease agents include those described, for example, in U.S. Pat. No. 3,531,285 of Haist et al., issued Sept. 29, 1970. Useful base-release agents include, for example, guanidinium salts, such as guanidinium trichloroacetate. quaternary ammonium malonates, certain amino acids, heat cleavable hydrazides, and oxazolidones, as described in U.S. Pat. No. 3,531,285.

When a base-release agent is employed in a photographic material according to the invention, a range of concentration can be employed as described. A useful concentration is typically about 0.25 mole to about moles of the base-release agent per mole of the photosensitive silver salt in the photographic material. A photothermographic composition or element according to the invention can accordingly comprise (a) photosensitive silver halide, (b) about 1 to about 4 moles of a silver halide developing agent per mole of such silver halide, (c) about 0.25 to about 4 moles of a 4-aryll-carbamoyl-2tetrazoline-5-thione stabilizer precursor, as described, per mole of said silver halide, (d) about 0.25 to about 10 moles of a base-release agent per mole of such silver halide, and (e) a polymeric binder.

The following examples are included for a further understanding of the invention.

EXAMPLE 1 This illustrates the preparation of 4-phenyl-1- phenylcarbamoyl-2-tetrazoline-5-thione.

To a partially dissolved solution of 17.8 g (0.100 mole) of 1-phenyl-2-tetrazoline-5-thione (also known as and referred to herein as PMT) in 300 m1 of benzene, 2 drops of heptamethylisobiguanide was added, followed by 12.5 g (0.105 mole) of phenylisocyanate. After the resulting mixture was refluxed for 2 hours the unreacted PMT was filtered off and the benzene solution was evaporated to dryness. The white paste was washed with anhydrous ether and recrystallized from a mixture of chloroform and carbon tetrachloride to yield 4.9 g (16.5%) of colorless needles, mp. 112-l 14C. There was no absorption shift in the UV spectrum from the original 2-tetrazoline-5-thione ring system, indicating substitution on the nitrogen atom of the PMT nucleus.

Analytical results calculated for C, 1-1, N 0S:C, 56.6; H, 3.7; S, 10.8.

Found: C, 56.6; H, 3.9; S, 10.9.

EXAMPLE 2 This illustrates the preparation of lcyclohexylcarbamoyl-4-phenyl-2-tetrazoline-S-thione.

A mixture of 17.8 g (0.100 mole) of PMT, 12.7 g (0.102 mole) of cyclohexylisocyanate and 4 drops of heptamethylisobiguanide in 350 ml of dichloromethane was allowed to stir for 42 hours at room temperature (about 20C. The resulting solution was evaporated at 30C.; the residue crystallized on standing. The crystalline residue was washed with 50 ml of ligroin and then dissolved in 200 ml of carbon tetrachloride. After the solution was treated with molecular sieves and charcoal, 250 ml of ligroin was added. The white solid (unreacted PMT) was removed by filtration and washed with 50 ml of carbon tetrachloride followed by ml of ligroin. The filtrate was set at room temperature for 1 hour to yield 13.0 g (43%) of colorless needles, mp. 89-93C.

Analytical results calculated for C H N OS: C, 55.6; H, 5.7; S, 10.6.

Found: C, 55.4; H, 5.7; S, 10.7.

EXAMPLE 3 This illustrates preparation of l-methylcarbamoyl-4- pheneyl-2-tetrazoline-5-thione.

A mixture of 35.6 g (0.20 mole) of PMT, 12.0 g (0.21 mole) of methylisocyanate and 2 drops of heptamethylisobiguanide in 600 ml of tetrahydrofuran was allowed to stir for 48 hours at room temperature (about 20C.). The resulting solution was treated with molecular sieves and charcoal and evaporated to dryness. The residue was recrystallized twice from carbon tetrachloride to yield 12.0 g (25.5%) of white solid, mp. 120.5-123.0C.

Analytical results calculated for C l-l N 0S: C, 45.9; H, 3.8.

Found: C, 45.7; H, 3.8.

EXAMPLE 4 This illustrates preparation of 4-hexylcarbamoyl-lphenyl-2-tetrazoline-5-thione.

The procedure of Example 3, using hexylisocyanate in place of the methylisocyanate, gave an oily compound. N 1.5673, with a conforming nmr and UV spectrum.

Analytical results calculated for Found: C, 54.8; H, 6.3.

EXAMPLE 5 This illustrates preparation of N,N'- hexamethylenebis( 1-carbamoyl-4-phenyl-2tetrazoline 5-thione).

To a partial solution of 356 g (2.0 mole) of PMT in 6.5 liters of dichloromethane was added 10 drops of heptamethylisobiguanide and a solution of 168.2 g 1.0 mole) of hexamethylene diisocyanate in 500 ml of dichloromethane within 5 minutes. After it was refluxed for 5 hours, the reaction mixture was left at room temperature overnight. Treatment with molecular sieves and charcoal gave a green-colored solution which was evaporated to dryness and the residue slurried with 2 liters of anhydrous ether to yield 383 g of white solid, mp 1 13-1 18C., which after recrystallization melted at 116.0117.5C.

Analytical results calculated for Found: C, 50.7; H, 4.9.

EXAMPLE 6 This is a comparative example.

A silver behenate-behenic acid dispersion A was pre pared by ball-milling the following components for approximately 112 hours:

silver behenate 168.0 g behenic acid 64.0 g lithium stearate 16.8 g poly(vinyl butyral) 120.0 g acetone-toluene (1:1 by volume) 2.0 iters A photothermographic composition was prepared by combining the following addenda:

silver behenate-behenic acid 63.0 ml dispersion A (preparation described above) lytvinyl butyrall-silver 20.0 ml i omoiodide emulsion (6 mole l. 6 limole Ag,

100 g polymer/mole Ag) acetone-toluene-methanol (1:1:1 by 1 1.0 ml volume) solution containing 0.5% by weight of N-hydroxy l,8- naphthalimide acetone-methanol solution (33:1 by 0.6 ml volume) containing 3-carboxymethyl 5-[(3-methy1-2-thiazolidinylidene)-1- methylethylidenelrhodanine and 0.1% by volume trietbylamine acetone solution containing 10% by 10.0 ml weight 2,6-dichloro-4-benzenesulfonamidophenol acetone 18.0 ml

The above composition was coated on a suitable paper support at 0.86 g Ag per square meter of support. This control coating was imagewise exposed to tungsten light for 0.5 second, overall heated at 130C. for 2 seconds and then subjected to fluorescent roomlight for 15 minutes. The sensitometric results are given in following Table 1.

EXAMPLE 7 A photothermographic element was prepared in the manner of Example 6 except that the final coating composition now contained 8 ml of an acetone solution containing 1% by weight N,N'-hexamethylenebis(lcarbamoyl-4-phenyl-2-tetrazoline-5-thione). (See Example 5). This thione compound was mixed into the coating composition prior to coating onto the layer support. Exposing and processing procedures were as described in Example 6. The sensitometric results are shown in Table 1.

Table l 15 Minute Print-U6 Background Example D A Tone* 6 0.32 1.13 0.81 Pale magenta (comparative example) 7 0.26 1.00 0.74 Gray (invention) AD: DIIIAJDIIYIII The background tone changed from pale magenta in Example 6 to a grayish cast in Example 7 with no significant change in image discrimination.

EXAMPLE 8 silver behenate-behenic acid A (preparation described previously) acetone solution containing 0.1 mg/ml of 3-ethyI-S'I(3-ethyl-2-benzothiazolinylidene 1 -methylethylidene1-2-thio-2,4-oxazolidinedione acetone solution containing 10% by weight 2,6-dichloro-4-benzene sulfonamidophenol l :1 :1 acetone-toluene-methanol solution containing 0.5% by weight N-hydrox -l ,S-naphthalimide poly(viny butyral)-silver bromoiodide emulsion (6 mole l, 6 llmole Ag, g polymer/mole Ag) acetone-toluene (1:1 by volume) The dried coating was imagewise exposed to tungsten light, and the individual samples were processed by contacting them with a heated metal block for 2 seconds at C, C, C, C., and C. respectively. The minimum densities are read with a blue filter and the results listed in following Table 1].

EXAMPLE 9 Example 8 was repeated except that the final coating composition contained 4.0 m1 of an acetone solution containing 2% by weight of the carbamoyl compound described in Example 5. Exposing and processing procedures were as described in Example 8; see Table [1 for the sensitometric results.

Table ll Minimum Densities Example 1 10C 120C 130C 140C 150C 8 0.12 0.18 0.23 0.28 0.60 (comparative example) 9 0.12 0.22 0.26 0.25 0.37 (invention) Results similar to Example 9 are provided when each of the following carbamoyl substituted tetrazolinethiones are employed in place of the compound of Example EXAMPLE l0 4-phenyll-phenylcarbamoyl-2-tetrazoline-5-thione EXAMPLE 1 l l-cyclohexylcarbamoyl-4-phenyl-Z-tetrazoline-S- thione EXAMPLE l2 l-methylcarbamoyl-4-phenyl-2-tetrazoline-5-thione EXAMPLE l3 l-hexylcarbamoyl-4-phenyl-Z-tetrazoline-S-thione EXAMPLE 14 This is a comparative example.

A silver behenatebehenic acid dispersion was pre pared by ball-milling the following components for approximately 72 hours:

si ver hehenate l68 g hehenic acid 64 g lithium stearate l6.8 g polylvinyl butyral) I ucetonetoluene 1:] by volume) 2 liters A photothermographic material was prepared by combining the following addenda with 71 ml of the above dispersion, mixing thoroughly and coating at 0.86 g Ag/m.

The resulting photothermographic element was exposed imagewise for 0.5 seconds to tungsten light. The exposed photothermographic element was then overall heated by holding the element against a heated metal block for 2 seconds at l30C. The following Table ll] provides the sensitometric results for the described photothermographic material.

EXAMPLE IS The procedure described in Example l4 was repeated with the exception that the composition contained 2.5 ml of an acetone solution containing 3% by weight of l-cyclohexylcarbamoyl-4-phenyl-Z-tetrazoline-S-thione.

The resulting photothermographic element was imagewise exposed and overall heated to provide a developed and stabilized image. The sensitometric results are described in Table III following.

EXAMPLE [6 This is a comparative example.

The procedure set out in Example 14 was repeated with the exception that the composition contained 5.77 ml of an acetone solution containing l% by weight of S-methoxycarbonylthio- 1 -phenyltetrazole.

The resulting photothermographic element was imagewise exposed and overall heated as described in Example 14. The sensitometric results are described in following Table Ill.

The procedure set out in Examples l4, l5 and 16 was repeated with the exception that the imagewise exposed and heat processed photothermographic elements were subjected to ft. candles of light for 20 minutes.

Part of these samples were stored for 3 days at 378C. and 50% relative humidity and then imagewise exposed and heat processed. The sensitometric results from these procedures are also set out in following Table III.

The results in Table 1]] illustrate that the stabilizer precursors of the invention provide improved protection against print-out density formation due to roomlight handling of heat processed elements and that the photothermographic elements according to the invention provide improved stability compared to a photothermographic element containing an image stabilizer precursor described in Belgian Pat. No. 768,071.

AD Mr min The minimum density lD,,,;,,) values illustrate the stabilizer precursor of Example l5 provides reduced minimum density compared to the control of Example l4 after the described post-processing exposure to light and humidity. Also the results of Examples l5 and lb illustrate that after 3 days at 37.8C. and 50% relative humidity that the stabilizer precursor of Example l5 provides surprisingly higher maximum density and AD [the difference between D and D,,.,,) compared to the prior art compound of Example If).

EXAMPLE l7 The following example illustrates a photothermographic material according to the invention comprising a base-release agent as described: a composition is pre pared by mixing hydroquinone. 4-methyl-4- hydroxymethyll -phenyl-3-pyrazolidone. guanidium trichloroacetate, p0ly( vinyl alcohol) binder in alcohol and water as described in Example I of U.S. Pat. No. 3,531,285 of Haist et 211., issued Sept. 29, 1970. lcyclohexylcarbamoyl-4-phenyl-tetrazo1ine-5-thione is also added to the composition. The composition is coated on a photographic paper containing a gelatino, silver bromide photographic layer. Upon imagewise exposure to light following by overall heating the element to about 190C. for a few seconds a developed and stabilized image results.

If desired the described carbamoyl stabilizer precursors according to the invention can be used in combination with S-carbamoyl stabilizer precursors in photographic elements and compositions such as photothermographic materials. Useful S-carbamoyl stabilizer precursors are described in U.S. application Ser. No. 251,728 of Pierce et al, filed May 8, 1972.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

What is claimed is:

l. A heat stabilizable, photographic element comprising a support having thereon a photosensitive silver salt and a 4-aryl-l-carbamoyl-2-tetrazoline-5-thione stabilizer precursor.

2. A photographic element as in claim 1 also comprising a photosensitive silver salt-developing agent.

3. A photographic element as in claim 1 wherein said stabilizer precursor is a compound represented by the formula:

II NN c NH wherein R is aryl containing 6 to 12 carbon atoms and R is alkyl containing 1 to 12 carbon atoms, aryl containing 6 to 12 carbon atoms, cycloalkyl containing 3 to 8 carbon atoms when n is l; or alkylene containing 1 to 10 carbon atoms when n is 2; and n is 1 or 2.

4. A photographic element as in claim 1 wherein said stabilizer precursor is l-cyclohexylcarbamoyl-4- phenyl-2-tetrazoline-5-thione.

5. A photographic element as in claim 1 wherein said stabilizer precursor is N,N'-hexamethylenebis(1- carbamoyl-4-phenyl-2-tetrazoline-5-thione).

6. A photographic element as in claim 1 wherein said stabilizer precursor comprises about 0.009 mole to about 0.034 mole per mole of total silver in said photographic element.

7. A photographic element as in claim 1 wherein said photosensitive silver salt is photosensitive silver halide.

8. A photothermographic element comprising a support having thereon a layer comprising a photosensitive silver salt. a photosensitive silver salt developing agent and a 4'aryl-l-carbamoyl-2-tetrazoline-S-thione stabilizer precursor.

9. A photothermographic element as in claim 8 wherein said photosensitive silver salt is photosensitive silver halide.

10. In a photothermographic element comprising a support having thereon a layer comprising a. photosensitive silver halide, b. an oxidatiomreduction image-forming combination comprising i. a silver salt oxidizing agent with ii. a reducing agent,

0. a polymeric binder, and

d. a thione. image stabilizer precursor, the improvement wherein said stabilizer precursor comprises a 4-aryll -carbamoyl-Z-tetrazoline-S-thione.

11. A photothermographic element as in claim 10 wherein said 4-aryl-1-carbamoyl-2-tetrazoline-5-thione stabilizer precursor is a compound represented by the structure:

O A IT1ITI M c NH-iiz' N c s \N/ n wherein R is aryl containing 6 to 12 carbon atoms and R is alkyl containing 1 to 12 carbon atoms, aryl containing 6 to 12 carbon atoms. cycloalkyl containing 3 to 8 carbon atoms when n is l; or alkylene containing l to 6 carbon atoms when n is 2; and n is l or 2.

12. A photothermographic element as in claim 10 wherein said stabilizer precursor is lcyclohexylcarbamoyl-4-phenyl-2-tetrazoline-5-thionc.

13. A photothermographic element as in claim 10 wherein said stabilizer precursor is N,N'- hexamethylenebis( l-carbamoyl-4-phenyl-2-tetrazoline-5-thione.

14. A photothermographic element as in claim 10 wherein said stabilizer precursor comprises about 0.009 mole to about 0.034 mole per mole of total silver in said photothermographic element.

15. A photothermograhic element as in claim 10 also comprising an activator-toning agent.

16. A photothermograhic element comprising a support having thereon a layer comprising a. photosensitive silver halide,

b. an oxidation-reduction image-forming combination comprising i. silver behenate, with ii. a sulfonamidophenol reducing agent,

c. a poly(vinyl butyral) binder,

d. a spectral sensitizing dye,

e. a succinimide or N-hydroxynaphthalimide activator-toning agent, and

f. l-cyclohexylcarbamoyl-4-phenyI-Z-tetrazoline-S- thione.

17. A photographic composition comprising a photosensitive silver salt, a 4-aryl-l-carbamoyl-2-tetrazoline- S-thione stabilizer precursor and a polymeric binder.

18. A photographic composition as in claim 17 also comprising a photosensitive silver salt, developing agent.

19. A photographic composition as in claim 17 wherein said photosensitive silver salt is photosensitive silver halide.

20. A photographic composition comprising (a) photosensitive silver halide, (b) a stabilizer precursor represented by the formula:

wherein R is aryl containing 6 to l2 carbon atoms and R is alkyl containing 1 to 12 carbon atoms, aryl containing 6 to 12 carbon atoms, cycloalkyl containing 3 to 8 carbon atoms when n is l; or alkylene containing 1 to 6 carbon atoms when n is 2; n is 1 or 2; and (c) a polymeric binder.

21. A photographic composition as in claim 20 wherein said stabilizer precursor comprises about 0.009 mole to about 0.034 mole per mole of total silver in said photographic composition.

22. Aa photographic composition comprising (a) photosensitive silver halide, (b) a stabilizer precursor comprising l-cyclohexylcarbamoyl-4-phenyl-2-tetrazoline-S-thione and (c) poly(vinyl butyral).

23. A photographic composition comprising (a) photosensitive silver halide, (b) a stabilizer precursor comprising N,N '-hexamethylenebis( l-carbamoyl-4-phenyl- Z-tetrazoline-S-thione) and (c) poly(vinyl butyral).

24. A photothermographic composition comprising (a) photosensitive silver salt, (b) a photosensitive silver salt developing agent, (c) a 4-aryl-l carbamoyl-2-tetrazoline-S-thione stabilizer precursor, (d) a baserelease agent, and (e) a polymeric binder.

25. A photothermographic composition as in claim 24 comprising (a) photosensitive silver halide, (b) a silver halide developing agent, (c) a stabilizer precursor comprising l-cyclohexylcarbamoyl-4-phenyl-2-tetrazoline-5-thione, (d) a base-release agent and (e) a polymeric binder.

26. A photothermographic composition as in claim 24 comprising (a) photosensitive silver halide, (b) about I to about 4 moles of a silver halide developing agent per mole of said silver halide, (c) agent 0.25 to about 4 moles of a 4-aryl-l-carbamoyl-2-tetrazoline-5- thione stabilizer precursor per mole of said silver halide. (d) about 0.25 to about moles ofa base-release agent per mole of said silver halide, and (e) a polymeric binder.

27. A photothermographic composition comprising (a) photosensitive silver halide, (b) an oxidationreduction image-forming combination comprising i. a silver salt oxidizing agent with ii. a reducing agent,

(c) a polymeric binder, and (d) a 4-aryI-l-carbamoyl- 2-tetrazoline-5-thione stabilizer precursor.

28. A photothermographic composition as in claaim 27 wherein said 4-aryl-l-carbamoyl- Z-tetrazoline-S- thione stabilizer precursor is a compound represented by the structure:

wherein R is aryl containing 6 to l2 carbon atoms and R is alkyl containing l to 12 carbon atoms, aryl containing 6 to [2 carbon atoms, cycloalkyl containing 3 to 8 carbon atoms when n is l; or alkylene containing l to 6 carbon atoms when n is 2; and n is l or 2.

29. A photothermographic composition as in claim 27 wherein said stabilizer precursor is lcyclohexylcarbamoyl-4 phenyl-Z-tetrazoline-5-thione.

30. A photothermographic composition as in claim 27 wherein said stabilizer precursor is N,N hexamethylenebis( l-carbamoyl-4-phenyl-2-tetrazoline-S-thione.

31. A photothermographic composition as in claim 27 wherein said stabilizer precursor comprises about 0.009 mole to about 0.034 mole per mole of total silver in said photothermographic composition.

32. A photothermographic composition as in claim 27 also comprising an activator-toning agent.

33. A photothermographic composition comprising a. photosensitive silver halide,

b. an oxidation-reduction image-forming combination comprising i. silver behenate, with ii. a sulfonamidophenol reducing agent,

0. a poly(vinyl butyral) binder,

d. a spectral sensitizing dye,

e. a succinimide or N-hydroxynaphthalimide activator-toning agent and f. a stabilizer precursor comprising cyclohexylcarbamoyl-4-phenyl-2-tetrazoline.

34. A process of stabilizing an image in a photothermographic element comprising a support having thereon a photosensitive silver salt and a 4-aryl-lcarbamoyl-2-tetrazoline-5-thione, comprising heating said element to about to about 250C.

35. A process as in claim 34 comprising heating said element for about 1 to about 60 seconds.

36. A process of developing and stabilizing an image in a photothermographic element comprising a support having thereon a layer comprising a. photosensitive silver halide,

b. an oxidation-reduction image-forming combination comprising i. a silver salt oxidizing agent with ii. a reducing agent, c. a polymeric binder, and d. a thione, image stabilizer precursor comprising a 4-aryll -carbamoyl-2-tetrazoline-5-thione, comprising heating said element to about 80 to about 250C.

37. A process as in claim 36 comprising heating said element for about l to about 60 seconds.

38. A process of developing and stabilizing an image in a photothermographic element comprising a support having thereon a layer comprising a. photosensitive silver halide,

b. an oxidation-reduction image-forming combination comprising i. silver behenate with ii. a sulfonamidophenol reducing agent,

c. a poly(vinyl butyral) binder,

d. a succinimide or N-hydroxynaphthalimide activator-toning agent,

e. a sensitizing dye, and

f. a thione, image stabilizer precursor comprising a 4-aryl-1-carbamoyl-2-tetrazoline-5-thione, comprising heating said element to about to about l75C. for about l to about 10 seconds.

UNITED STATES PATENT AND TRADEMARK OTFICE CERTIFICATE OF CORRECTION PATENT NO. 3,893, 59 DATED July 8, 1975 INVENTOR(S) D. M. Burness, H. G. Ling and R. H. Ericson It is certified that error appears in the ab0ve-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, lines 29-30, "photothermograhic" should read --photothermographic-.

Column 2, line 32, "photothermograhic" should read ---photothermographic--.

Column 5, line 35, ul'mrashhed should read --unwashed---; and,

line #0, "photothermograhic" should read --photothermo graphic-.

Column 7, line 7, discrimation" should read ---discrimination Column 8, line 67, "amd" should read ---and--.

Column 10, line 49, that part of formula reading pheneyl should read ---phenyl---.

Column 12, line #7, "the" should read --then--.

Column l r, line 53, "guanidium" should read -guanidinium--.

Column 16, line 29, "photothermograhic" should read ---photothermographic---.

Column 17, line 5, "Aa" should read --A---; line 27',

"agent" second occurrence, should read ---about--; and line rO, "claaim" should read ---c1aim---.

Signed and Scaled this A ttes t:

RUTH C. MASON C. MARSH A lfsting 0 AU D mmm'ssiunvr njlatents and Trademarks 

1. A heat stabilizable, photographic element comprising a support having thereon a photosensitive silver salt and a 4-aryl-1-carbamoyl-2-tetrazoline-5-thione stabilizer precursor.
 2. A photographic element as in claim 1 also comprising a photosensitive silver salt-developing agent.
 3. A photographic element as in claim 1 wherein said stabilizer precursor is a compound represented by the formula:
 4. A photographic element as in claim 1 wherein said stabilizer precursor is 1-cyclohexylcarbamoyl-4-phenyl-2-tetrazoline-5-thione.
 5. A photographic element as in claim 1 wherein said stabilizer precursor is N,N''-hexamethylenebis(1-carbamoyl-4-phenyl-2-tetrazoline-5-thione).
 6. A photographic element as in claim 1 wherein said stabilizer precursor comprises about 0.009 mole to about 0.034 mole per mole of total silver in said photographic element.
 7. A photographic element as in claim 1 wherein said photosensitive silver salt is photosensitive silver halide.
 8. A photothermographic element comprising a support having thereon a layer comprising a photosensitive silver salt, a photosensitive silver salt developing agent and a 4-aryl-1-carbamoyl-2-tetrazoline-5-thione stabilizer precursor.
 9. A photothermographic element as in claim 8 wherein said photosensitive silver salt is photosensitive silver halide.
 10. IN A PHOTOTHERMOGRAPHIC ELEMENT COMPRISING A SUPPORT HAVING THEREON A LAYER COMPRISING A. PHOTOSENSITIVE SILVER HALIDE, B. AN OXIDATION-REDUCTION IMAGE-FORMING COMBINATION COMPRISING I. A SILVER SALT OXIDIZING AGENT WITH II. A REDUCING AGENT, C. A POLYMERIC BINDER, AND D. A THIONE, IMAGE STABLIZER PRECURSOR, THE IMPROVEMENT WHEREIN SAID STABILIZER PRECURSOR COMPRISES A 4-ARYL-1CARBAMOYL-2-TETRAZOLINE-5-THIONE,
 11. A photothermographic element as in claim 10 wherein said 4-aryl-1-carbamoyl-2-tetrazoline-5-thione stabilizer precursor is a compound represented by the structure:
 12. A photothermographic element as in claim 10 wherein said stabilizer precursor is 1-cyclohexylcarbamoyl-4-phenyl-2-tetrazoline-5-thione.
 13. A photothermographic element as in claim 10 wherein said stabilizer precursor is N,N''-hexamethylenebis(1-carbamoyl-4-phenyl-2-tetrazoline-5-thione.
 14. A photothermographic element as in claim 10 wherein said stabilizer precursor comprises about 0.009 mole to about 0.034 mole per mole of total silver in said photothermographic element.
 15. A photothermograhic eleMent as in claim 10 also comprising an activator-toning agent.
 16. A photothermograhic element comprising a support having thereon a layer comprising a. photosensitive silver halide, b. an oxidation-reduction image-forming combination comprising i. silver behenate, with ii. a sulfonamidophenol reducing agent, c. a poly(vinyl butyral) binder, d. a spectral sensitizing dye, e. a succinimide or N-hydroxynaphthalimide activator-toning agent, and f. 1-cyclohexylcarbamoyl-4-phenyl-2-tetrazoline-5-thione.
 17. A photographic composition comprising a photosensitive silver salt, a 4-aryl-1-carbamoyl-2-tetrazoline-5-thione stabilizer precursor and a polymeric binder.
 18. A photographic composition as in claim 17 also comprising a photosensitive silver salt, developing agent.
 19. A photographic composition as in claim 17 wherein said photosensitive silver salt is photosensitive silver halide.
 20. A PHOTOGRAPHIC COMPOSITION COMPRISING (A) PHOTOSENSITIVE SILVER HALIDE, (B) A STABILIZER PRECURSOR REPRESENTED BY THE FORMULA:
 21. A photographic composition as in claim 20 wherein said stabilizer precursor comprises about 0.009 mole to about 0.034 mole per mole of total silver in said photographic composition.
 22. Aa photographic composition comprising (a) photosensitive silver halide, (b) a stabilizer precursor comprising 1-cyclohexylcarbamoyl-4-phenyl-2-tetrazoline-5-thione and (c) poly(vinyl butyral).
 23. A photographic composition comprising (a) photosensitive silver halide, (b) a stabilizer precursor comprising N,N''-hexamethylenebis(1-carbamoyl-4-phenyl-2-tetrazoline-5-thione) and (c) poly(vinyl butyral).
 24. A photothermographic composition comprising (a) photosensitive silver salt, (b) a photosensitive silver salt developing agent, (c) a 4-aryl-1-carbamoyl-2-tetrazoline-5-thione stabilizer precursor, (d) a base-release agent, and (e) a polymeric binder.
 25. A photothermographic composition as in claim 24 comprising (a) photosensitive silver halide, (b) a silver halide developing agent, (c) a stabilizer precursor comprising 1-cyclohexylcarbamoyl-4-phenyl-2-tetrazoline-5-thione, (d) a base-release agent and (e) a polymeric binder.
 26. A photothermographic composition as in claim 24 comprising (a) photosensitive silver halide, (b) about 1 to about 4 moles of a silver halide developing agent per mole of said silver halide, (c) agent 0.25 to about 4 moles of a 4-aryl-1-carbamoyl-2-tetrazoline-5-thione stabilizer precursor per mole of said silver halide, (d) about 0.25 to about 10 moles of a base-release agent per mole of said silver halide, and (e) a polymeric binder.
 27. A photothermographic composition comprising (a) photosensitive silver halide, (b) an oxidation-reduction image-forming combination comprising i. a silver salt oxidizing agent with ii. a reducing agent, (c) a polymeric binder, and (d) a 4-aryl-1-carbamoyl-2-tetrazoline-5-thione stabilizer precursor.
 28. A photothermographic composition as in claaim 27 wherein said 4-aryl-1-carbamoyl- 2-tetrazoline-5-thione stabilizer precursor is a compound represented by the structure:
 29. A photothermographic composition as in claim 27 wherein said stabilizer precursor is 1-cyclohexylcarbamoyl-4-phenyl-2-tetrazoline-5-thione.
 30. A photothermographic composition as in claim 27 wherein said stabilizer precursor is N,N''-hexamethylenebis(1-carbamoyl-4-phenyl-2-tetrazoline-5-thione.
 31. A photothermographic composition as in claim 27 wherein said stabilizer precursor comprises about 0.009 mole to about 0.034 mole per mole of total silver in said photothermographic composition.
 32. A photothermographic composition as in claim 27 also comprising an activator-toning agent.
 33. A photothermographic composition comprising a. photosensitive silver halide, b. an oxidation-reduction image-forming combination comprising i. silver behenate, with ii. a sulfonamidophenol reducing agent, c. a poly(vinyl butyral) binder, d. a spectral sensitizing dye, e. a succinimide or N-hydroxynaphthalimide activator-toning agent and f. a stabilizer precursor comprising 1-cyclohexylcarbamoyl-4-phenyl-2-tetrazoline.
 34. A process of stabilizing an image in a photothermographic element comprising a support having thereon a photosensitive silver salt and a 4-aryl-1-carbamoyl-2-tetrazoline-5-thione, comprising heating said element to about 80* to about 250*C.
 35. A process as in claim 34 comprising heating said element for about 1 to about 60 seconds.
 36. A process of developing and stabilizing an image in a photothermographic element comprising a support having thereon a layer comprising a. photosensitive silver halide, b. an oxidation-reduction image-forming combination comprising i. a silver salt oxidizing agent with ii. a reducing agent, c. a polymeric binder, and d. a thione, image stabilizer precursor comprising a 4-aryl-1-carbamoyl-2-tetrazoline-5-thione, comprising heating said element to about 80* to about 250*C.
 37. A process as in claim 36 comprising heating said element for about 1 to about 60 seconds.
 38. A process of developing and stabilizing an image in a photothermographic element comprising a support having thereon a layer comprising a. photosensitive silver halide, b. an oxidation-reduction image-forming combination comprising i. silver behenate with ii. a sulfonamidophenol reducing agent, c. a poly(vinyl butyral) binder, d. a succinimide or N-hydroxynaphthalimide activator-toning agent, e. a sensitizing dye, and f. a thione, image stabilizer precursor comprising a 4-aryl-1-carbamoyl-2-tetrazoline-5-thione, comprising heating said element to about 100* to about 175*C. for about 1 to about 10 seconds. 